had one before, you are at higher risk, and if you travel a lot, the blood flow may be compressed, benning your legs like that, and with the concussion, one of the things she was told was to rest. not easy for her to do, i can tell you for a fact. that may be part of the inactivity. >> and we don't know what the cause is. back in 1998, it was deep vain thrombosis. >> dvt, a clot in one of the leg veins, in and of itself, not a problem, but it can break off and go to the lungs, called a pulmonary embolism, she is on blood thinners, and you treat the brain clot. this is within one of the blood vessels in her legs. they haven't told us. >> what do they do about this? once you have had an episode of dvt, what's the treatment? >> blood thinners, you want to tip the balance a little bit so you are more likely to break up the clot. the downside, rumor likely to bleed if you injure yourself. it's a careful balance and that's the monitoring in the hospital right now. >> i heard people say if you travel a lot you should take the low-dose aspirin is that true? >> baby aspirin. a lot of people take it